3.5 AS91391 Demonstrate understanding of the properties of organic compounds (5 credits)
IUPAC NAMING
NCEA PAST EXAM QUESTION: Write the IUPAC (systematic) names for the following organic substances
The tables below provide an overview of the molecules and year that they appeared in the NCEA Exam paper
The structure of aspartame (artificial sweetener) is given below. Identify the FOUR different functional groups within the aspartame molecule that are circled
Click on the solution and reasons for incorrect alternative IUPAC names here
NCEA PAST EXAM QUESTIONS on constitutional isomers and stereoisomers
Alanine is an amino acid. Its structure is shown below.
(a) (i) Describe the structural feature necessary for a compound to exist as enantiomers (optical isomers).
(ii) Identify one physical property that is the same for both enantiomers of alanine, and one that is different, clearly describing how this property could be used to distinguish between the enantiomers.
(b) Draw 3-D structures of the enantiomers of alanine.
When butan-2-ol undergoes a reaction with concentrated H2SO4, three possible organic products form, which are isomers of each other.
i) Draw the three isomers formed during this reaction.
ii) Which of the three isomers from part (i) will be formed in the smallest amount? Explain your answer.
a) The alcohol below can exist as two enantiomers (optical isomers).
i) Draw three-dimensional structures for the two enantiomers.
ii) Link the structure of enantiomers to a physical property that can be used to distinguish them from non-optically active molecules.
b) Draw the structural formulae of three different isomers of
• Isomer 1 turns moist blue litmus paper red.
• Isomer 2 is an ester.
• Isomer 3 is a ketone.
1) The amino acid alanine below can exist as two enantiomers (optical isomers).
i) Draw three-dimensional structures for the two enantiomers that clearly show the relationship between them.
ii) Alanine has two straight chain isomers that do not show acidic properties. One of these isomers, P, can exist as an enantiomer, the other isomer, Q,cannot. Draw P and Q.
iii) Explain why P exists as an enantiomer.
The amino acid alanine below can exist as two enantiomers (optical isomers).
i) Draw three-dimensional structures for the two enantiomers that clearly show the relationship between them
ii) Alanine has two straight chain isomers that do not show acidic properties. One of these isomers, P, can exist as an enantiomer, the other isomer, Q,cannot. Draw P and Q.
An alcohol A with the molecular formula C4H10O can exist as enantiomers (optical isomers).
i) State the structural requirement for a molecule to be able to exist as enantiomers.
ii) Describe a property of enantiomers that would enable them to be distinguished from each other.
iii) Draw the structural formulae of the enantiomers of alcohol A.
Compound A is a carboxylic acid with the molecular formula C4H8O2.
i) Draw the structural formula for the isomers of Compound A (they are an alkene, aldehyde and ester)
ii) Identify an isomer of Compound Athat can exist as a pair of enantiomers (optical isomers) and justify your choice
i) Draw a circle around the product of the reaction below that will show optical isomerism (exist as enantiomers). Give a reason for your answer.
ii) Explain how the two enantiomers of the compound circled above could be distinguished from each other.
a) C5H11OH is an example of an alcohol that can exist as a number of different isomers. Draw structures of the isomers of C5H11OH that satisfy the requirements of i) a branched-chain secondary alcohol (A) and ii) a branched-chain tertiary alcohol (B)
b)Explain why is the only primary alcohol isomer of C5H11OH that is able to exist as a pair of enantiomers (optical isomers).
i) Draw structural formulae for all the possible constitutional (structural) isomers of C4H10O that are alcohol
ii) Circle any isomer above that can exist as a pair of enantiomers (optical isomers).
iii) Explain what physical property would allow the two enantiomers to be distinguished.
Lactic acid is the common name for 2-hydroxypropanoic acid. Lactic acid can exist as enantiomers (optical isomers)
a) Draw three-dimensional structures for the two enantiomers of lactic acid that clearly show the relationship between them.
b) Compound X is a structural isomer of lactic acid. Compound X will turn blue litmus red but cannot exist as enantiomers.
i) Draw the structural formula for Compound X.
ii) Explain why this structure cannot exist as enantiomers
An alcohol (C4H10O) can exist as optical isomers (enantiomers).
i) Draw three-dimensional structures that show the relationship between the two enantiomers.
ii) Draw and name a structural (constitutional) isomer of
iii) Discuss the differences in chemical and physical properties between samples of these two structural isomers.
a) Compound A is an isomer of C4H8O and can exist as two enantiomers (optical isomers). It contains two different functional groups – an alcohol(OH–) group and an alkene group. Draw 3-dimensional structures for both enantiomers that clearly show the relationship between them.
b) Two compounds (B and C) have the same molecular formula, C4H8O. They are cis-trans isomers that contain a primary alcohol group. Both compounds rapidly decolourise bromine solution. Draw the structural formulae of compounds B and C.
i) Compound
can exist as two optical isomers (enantiomers).
Draw 3dimensional structures that clearly show the relationship between the two enantiomers.
ii) Describe similarities and differences in the chemical and physical properties of the enantiomers
A form of the polymer nylon can be made from the two monomers below.
(i) Draw the repeating unit of the polymer formed if these two monomers are used Consider the formation of this form of nylon in a laboratory.
(ii) Describe the type of reaction occurring, and explain why this reaction results in a polymer.
(iii) Explain why sebacoyl chloride is dissolved in a non-polar organic solvent rather than in water
(iv) Elaborate on the reaction that will occur if a dilute aqueous solution of acid is mixed with the newly formed polymer.
The following polymer will, under the correct conditions, hydrolyse.
i) Draw the monomer(s) from which this polymer is formed.
ii) Discuss the hydrolysis of the polymer.In your answer you should include:
• the conditions under which it can be hydrolysed
• structures of the organic products formed as a result of hydrolysis.
The structures of Polymer A and Polymer B are given below.
a) Draw the monomers from which these polymers are made.
b) One of the polymers from above can be hydrolysed using NaOH(aq). Identify the polymer and draw structures for the organic products of the hydrolysis.
c) Nylon 6,10 can be made from the monomers below.
Steps for the formation of Nylon 6,10 are given below:
1. 2 g of the diamine is dissolved in 25 mL of water.
2. 2.5 mL of sebacoyl chloride is dissolved in 25 mL of a non-polar organic solvent.
3. The dissolved sebacoyl chloride is poured into the diamine solution.
4. 5 g of NaHCO3 is added.
5. The nylon is extracted from the interface between the diamine and sebacoyl chloride layers.
• Identify the repeating unit of the polymer formed
• Explain why the diamine is water soluble.
• Explain why the sebacoyl chloride is dissolved in a non-polar organic solvent.
• Explain why NaHCO3 is added.
a) Nylon 6,6 is a polymer with the following structure:
i) Circle an amide linkage in the structure above.
ii) Draw TWO monomers that could have formed this polymer.
b) Nylon 6 is formed from the monomer H2N–(CH2)5–CO2H.
i) Name this monomer and draw THREE repeating units of the Nylon 6 polymer chain
ii) Nylon is used for making ropes for climbing and abseiling. The ropes come with a warning label attached, such as that shown below.
Discuss why this warning label is attached to nylon rope when purchased.
Include in your answer:
• the type of reaction that would occur
• relevant organic structural formulae
• any changes to the properties of the nylon rope.
The polymer commonly known as Kevlar is used to make bullet-proof vests and bicycle tyres. It can be made in a condensation reaction from either of the following pairs of monomers:
However, the second pair of monomers needs to be heated for the polymerisation reaction to take place.
Discuss these polymerisation reactions.
Your answer should include:
• a repeating unit of the polymer chain
• reasons for the choice of monomers
• identification of the functional group in the polymer
• a reason why this is classified as a condensation reaction
• a comparison of the two pairs of monomers, including the reason that the second reaction will not take place without heating.
a) Kodel is a polymer with the following structure:
i) Identify TWO monomers for this structure.
ii) Explain why this type of polymer is known as a condensation polymer.
b) Compound X is a polymer which can be hydrolysed to give a single monomer, Compound Y, which has the molecular formula C3H6O3.
Draw a section of the polymer, Compound X, showing at least two repeating units.
Lactic acidis able to form a condensation polymer in the presence of dilute sulfuric acid. Draw three repeating units of this polymer.
a) The reaction scheme below shows formation of a section of a nylon polymer chain. Complete the reaction scheme by:
i) identifying reagents 1, 2 and 3,
ii) drawing the structures of compounds P and Q,
iii) drawing a single repeating unit for the nylon polymer formed.
b) Nylon is used as a fibre to manufacture ropes and fabrics. These products can be damaged if they come into contact with acidic solutions.
Teflon is a polymer formed from F2C=CF2 and is not affected by contact with acidic solutions.
Discuss why nylon is affected by acidic solutions while Teflon is not. Use structural formulae and equations where appropriate.
Consider the following statement.
"Polyestersare polymers that can be made from two different monomers or from a single monomer"
Discuss this statement, using the structures of specific monomers and the polyesters that can be made from them, to illustrate your answer. Your answer should demonstrate a clear understanding of the highlighted terms.
Glycine and alanine can combine together with the elimination of a molecule of water to produce a dipeptide – as shown below
Look carefully, you’ll notice that glycine and alanine can combine to form a different dipeptide because a -H can be removed from the glycine and –OH from the alanine to from a different dipeptide and a water molecule. If three amino acids are joined together eg three molecules of glycine a tripeptide is formed.
If lots of amino acids are joined together (as in a protein chain), a polypeptide is formed.
NCEA PAST EXAM QUESTIONS on Amino Acids, dipeptides, tripeptides and proteins
Peptides are formed when amino acids combine.
(i) show two possible dipeptides that can be formed by combining the amino acids:
(ii) Circle the amide link in each dipeptide.
a) Glycine and serine are two amino acids, which can combine to form dipeptides.
i) Draw the structure(s) of the possible dipeptide(s) formed from a combination of glycine and serine.
ii) Explain your answer in terms of the structure and functional groups present in the amino acids and in the dipeptide(s).
b) Determine the products of hydrolysis of the molecule shown below in BOTH acidic and basic conditions. Justify your answer in terms of structure and reactivity.
Amino acids are the building blocks that make up proteins. Alanine and valine are amino acids which can combine to form dipeptides.
a) Draw the structure of a possible dipeptide formed from the combination of alanine and valine.b) Draw the organic products of the hydrolysis of the dipeptide below using : i) dilute hydrochloric acid solution ii) dilute sodium hydroxide solution.
a) Gluthathione (GSH) is one of the most common small peptides in animals, plants and bacteria
i) Draw a circle around one of the amide (peptide) groups.
ii) Draw structures of the products of the hydrolysis of this compound using alkaline conditions (NaOH) and compare with the structures of the hydrolysis products under acidic conditions.
Compoundundergoes a condensation reaction with the following molecule (commonly referred to as alanine). It forms two different organic products referred to as dipeptides.
i) Draw the structural formulae for the two possible dipeptides.
ii) Explain why the formation of dipeptides is referred to as a ‘condensation reaction’.
(i) Circle one of the alkene groups in the triglyceride molecule.
(ii) This triglyceride is described as unsaturated. Describe a chemical test that can be used to show that the molecule is unsaturated. Give any observations, and state the type of reaction occurring.
(iii) Draw the structural formulae of the organic products formed by hydrolysis of this triglyceride using aqueous sodium hydroxide.
The triglyceride below is shown in condensed form.
(i) Circle a functional group on the diagram above and give its name.
(ii) Compare and contrast the reaction of the above triglyceride when it undergoes both acidic and basic hydrolysis. In your answer you should include:
• drawings of condensed structures of the organic products
• any reagents and conditions required for the reaction to proceed.
Give the structures and names of the products of the reactions below. These reactions are carried out by heating in either:
• dilute hydrochloric acid solution, or
• dilute sodium hydroxide solution.
Discuss the similarities and differences in the reactions of methyl propanoate, CH3CH2COOCH3, in basic conditions with NaOH, and in acidic conditions with HCl.
In your answer you must:
• describe the type of reaction
• write equations showing structural formulae for reactions occurring.
A triglyceride found in olive oil has the following structure:
i) Put a circle around one of the ester groups in the triglyceride molecule shown above.
ii) This triglyceride is described as being an unsaturated molecule, which means that it contains carbon to-carbon bonds, which are not single bonds.
Bromine water can be used to confirm that this triglyceride is unsaturated. Describe the observations when bromine water is reacted with this triglyceride.
iii) Draw the structural formulae of the products produced by the hydrolysis of this triglyceride in basic conditions, using aqueous sodium hydroxide, NaOH.
i) For the molecule below, circle the ester functional group and put a square around the alkene functional group.
ii) Complete the equation below to show the structural formulae of the two organic reactants used in the preparation of 2-methyl propenoate.
iii) 2-methyl propenoate will react with HCl to give two different haloalkane products. Draw the structural formulae of the haloalkane products.
1) Esters are often responsible for the flavouring of fruit. The compound below is an ester with a raspberry flavour.
Esters can be prepared by refluxing the reactants with a small amount of concentrated sulfuric acid. After refluxing, the reaction mixture is treated with potassium carbonate and distilled.
Discuss the preparation of the ester shown above. Your answer should include:
• an appropriate chemical equation for the formation of the ester
• the reason for using the chemicals stated in bold above
• a discussion of why reflux and distillation are used in this preparation.
2) The triglyceride shown below was heated with aqueous sodium hydroxide, NaOH. Draw the structural formulae of the two products formed in this reaction.
A triglyceride found in cocoa butter has the following structure.
a) Complete the equation below, which shows hydrolysis of this triglyceride in acidic conditions using H2SO4 solution.
b) Compare the products that would form if the hydrolysis occurred in basic conditions using NaOH solution
Palm oil contains the triglyceride with the structure shown below. It forms when glycerol (an alcohol) and palmitic acid (a carboxylic acid) react together.
a) Use the diagram above to deduce the structural formulae of glycerol and palmitic acid. Draw them in the spaces below.
b) The triglyceride shown above can undergo hydrolysis in acidic or basic conditions. How will the different hydrolysis conditions affect the products of the reaction?
Fats and oils are triester molecules. Hydrolysis of a fat can be represented by the equation below.
a) Circle ONE of the ester groups in the fat.
b) Write the name of the functional group that would be present in compound M.
c) Unsaturated fats are usually considered to be healthier than saturated fats. What is meant by the term unsaturated?
d) Describe a test, using a solution of bromine in a non-polar solvent, that could be carried out in the laboratory to compare the degree of unsaturation of two fats.
NCEA PAST EXAM QUESTION: Distinguishing between organic compounds
Identify the reagents, conditions required, and observations linked to species, to enable the following pairs of chemicals to be distinguished from each other.
(i) Aqueous solutions of propanamine and propanamide.
(ii) Propanone and propanal.
(iii) Propanoyl chloride and propyl propanoate.
1) Devise a method for distinguishing between the three liquid compounds, butan-1-ol, butanoic acid, and butanoyl chloride, using only blue litmus paper and water.
Explain each of the observations in your method, with reference to the structure of the organic compounds.
2) Describe how you could distinguish between methylpropan-2-ol and butan-1-ol and butan-2-ol , using chemical tests on the alcohols and / or their oxidation products
Explain a laboratory procedure that would allow the following pairs of compounds to be distinguished. In your answers, you should include:
the reagent used
the expected result for any reactions that may or may not occur
the structural formulae of the organic product(s) formed when the reaction(s) occur.
Explain a laboratory procedure that would allow the following pairs of compounds to be distinguished. In your answers, you should include:
the reagent used
the expected result for any reactions that may or may not occur
the structural formulae of the organic product(s) formed when the reaction(s) occur.
Describe a test that could distinguish between an amide and an amine
1) Explain how you could distinguish from propanone
Your explanation should include:
• the reagents used and the conditions needed
• the expected observations.
2) Compound X, an isomer of Compound A, C3H6O3, can exist as enantiomers. It reacts with acidified dichromate solution to give Compound Y, C3H4O3. Both compounds X and Y react with sodium carbonate to produce carbon dioxide gas. Identify Compounds X and Y and justify your answers in relation to the information above.
1) A colourless liquid is known to be a branched-chain alcohol with the molecular formula C5H11OH. Investigations of this liquid show the following
features:
• It does not rotate the plane of polarised light.
• It reacts with acidified potassium dichromate solution.
• It reacts with concentrated sulfuric acid. The product of this reaction decolourises bromine water.
Use the features listed to determine which of the alcohols A to E is the colourless liquid. Justify your answer.
2) Devise a method for distinguishing between propanoyl chloride, 2-amino-3-methylbutane, pentanal, 4-chlorobutanoic acid. Each test should use either moist red litmus paper or an acidified solution of potassium permanganate
Discuss how to test propanal and propanoic acid to demonstrate that they are different from each other AND different from propan-1-ol. Include the observations that would allow each substance to be identified as a result of these tests.
1) The identity of a colourless liquid is unknown. It is thought to be one of the following: ethanoyl chloride (CH3COCl) or ethanol (CH3CH2OH) or 2-methyl propan-2-ol ((CH3)3COH) or hex-1-ene (CH2= CHCH2CH2CH2CH3).
Devise a scheme using bromine water and acidified dichromate to identify the colourless liquid.
Describe the observations expected at each stage (equations not required).
Describe a chemical test that would distinguish between each of the following pairs of substances. For each test, identify the reagents used, and link the observations to any reactions that may or may not occur.
Describe chemical tests that could be used to distinguish between the compounds in each of the pairs of substances below. For each test description:
• include reagents used, and
• link the observed results to the reactions occurring at the functional groups present in the organic molecules.
There is no Crystal Ball Activity for Level 3 distinguishing between organic substances because once you have complete all the questions above you'll be sweet with them.
Organic reaction pathways
Download, print the charts above, then stick to the back of your toilet door, take a break, clear a blockage and learn your Organic Reaction pathways
NCEA PAST EXAM QUESTIONS on Reaction pathways and reagents
Complete the following reaction scheme by drawing the structural formulae of the organic compounds A to E, and identifying reagents 1 to 5.
Propene can be reacted with water in the presence of acid to form a major product (A) and a minor product (B).
• A is oxidised to form product C.
• B is oxidised to form product D.
• When D is reacted with SOCl2, it forms product E.
• When D is reacted with alcohol B, it forms an ester G.
• When D is reacted with alcohol A, it forms ester H, which is an isomer of G.
• When E is reacted with alcoholic ammonia, it forms product F.
• When E is reacted with water, it forms product D.
1) For the following conversions, identify the reagent required, and state the type of reaction occurring.
(i) Pentan-2-one is converted to pentan-2-ol.
(ii) Butan-2-ol is converted to a mixture of but-1-ene and but-2-ene.
(iii) Discuss the reaction occurring in (ii) above, with reference to the structures of the organic reactant and products.
2) Complete the following reaction scheme by drawing the structural formulae of the organic compounds B and C, and identifying reagent 1.
Include any necessary conditions, needed to bring about the transformation from reactant A to the organic compound C, which is a base.
3)
When ammonia reacts with two products are formed.Complete the equation below by naming compounds or drawing the structure.
1) For the following conversion, identify the reagent required and state the type of reaction occurring. You should give a reason for your answer in terms of the structure of the reactants and products.
2)a) Complete the following reaction scheme that shows some reactions starting with butanal. Give the structural formulae of the organic products A, B,and C.
b) Devise and complete the reaction scheme starting with butanone in place of butanal to show how butanone would react with the reactants 1–3. In your answer, you should:
identify the products formed in each reaction step; state if no reaction occurs
write the structural formula for each product formed, including major and minor products (if any).
c) Compare and contrast the two reaction schemes. In your answer, justify the reasons for
the similarities and the differences between these two schemes
the products formed in each reaction.
4) Use the following information to answer this question.
Compound W is a branched chain molecule with a molecular formula C4H10O. When Compound W is heated with excess acidified potassium dichromate it is readily oxidised to Compound X, which has acidic properties A substitution reaction occurs when Compound X is reacted with SOCl2. The molecular formula of Compound Y isC4H7OCl When Compound Y reacts with aminomethane, CH3–NH2, a substitution reaction occurs and Compound Z forms
Determine the structural formulae of Compounds W, X, Y, and Z.
Justify your answer by explaining how you arrived at these structures from the information given above. In your answer, you should:
include other possible structural formulae you considered
give your reasons for rejecting the other structural formulae.
1) The haloalkane 1-chlorobutane can be used to make butanamide. One of the intermediate products is a carboxylic acid. Show, using structural formulae, how this might be achieved in a number of reaction steps. Include all reagents
2) Alcohol A, (C4H10O) can react with Cr2O72– / H+ to give compound B which does not react with Tollens’ reagent. Compound A also reacts with SOCl2 to give a haloalkane C, which when reacted with alcoholic KOH, gives two products, D and E, which are not geometric isomers. When E reacts with H+ / H2O, A is the product. When D reacts with H+ / H2O, two products are formed, A and F. F can be oxidised to form butanoic acid. Give the structural formulae AND names for each of the compounds A to F.
Complete the following reaction scheme by naming and drawing the structural formula of each of the compounds A to F. Identify the reagents 1 to 4, including any necessary conditions, needed to bring about each transformation.
The haloalkane, 2-chloro-2-methylbutane, can be prepared by reacting 2-methylbutan-2-ol with concentrated HCl.i) Write an equation for this reaction using structural formulae.ii) State the type of reaction occurring, and give a reason for your answer.
1) Identify the compound from these given: propanoyl chloride, 2-amino-3-methylbutane, pentanal, 4-chlorobutanoic acid that will react as described below, and draw the structural formula for each organic product formed.
Elimination with alcoholic KOH
Oxidation with Fehling’s or Benedict’s solution
Substitution with aqueous KOH
2) Complete the reaction scheme by giving the formulae for reagents 1 to 4 and the structural formulae for the organic products A to D.
Complete the following reaction scheme by giving the formulae for reagents 1 to 5 and the structural formulae for the THREE organic products.
2-bromobutane reacts by substitution to form 2-butanol. However, if the reaction conditions are changed, an elimination reaction occurs. There are two possible products for the elimination reaction. Complete the following reaction scheme by indicating the reagents in the shaded boxes and the organic products in the other boxes for each of these reactions of 2-bromobutane.
Complete each of the equations below by writing the organic product in the blank boxes and the reagent needed in the shaded boxes.
For each reaction below, identify: (i) the type of reaction, (ii) the reagent required to carry out the reaction.
a) Complete the reaction scheme below by:
i) identifying the three reagents
ii) drawing the structures of compounds X and Y
iii) naming organic compounds X and Y, and the compound with formula CH3CH2COCl
b) Each of the parts (i) – (iii) below refers to one step in the reaction scheme on page 2. For each part, identify the type of reaction (from the given list: addition, elimination, oxidation, polymerisation, substitution) and use the reaction in that step to explain the term.
i) 2-chloropropane is converted to propene.
ii) Compound X (the minor product) is converted to propan-1-ol.
iii) Propan-1-ol is converted to propanoic acid.
c) When HBr is reacted with propene, there are two possible products. Discuss how the compounds formed in this reaction scheme would vary if these two products were not separated before reagent 2 is added
.
The following reactions involve the loss of water. Clearly show the structure of one major organic product of each of these reactions.
NCEA PAST EXAM QUESTION: Describe and Explain Practical Procedures in Organic Chemistry
Explain why the equipment below is used for hydrolysis of a triglyceride.
Instructions for the preparation of 2-chloro-2-methylpropane are given below. Read the instructions carefully and answer the questions that follow.
1. Shake 10 mL of 2-methylpropan-2-ol with 30 mL of concentrated hydrochloric acid in a separating funnel for 10 minutes.
2. Run off the bottom acid layer and discard it. Add saturated sodium hydrogen carbonate to the organic product. Shake, releasing the tap every few seconds to relieve the pressure.
3. Run off the bottom aqueous layer and discard it. Transfer into a conical flask and add some anhydrous sodium sulfate, and stir thoroughly.
4. Transfer the organic product into a round-bottom flask, and collect the fraction boiling within 2oC of the boiling point of 2-chloro-2-methylpropane.
(i) Explain why the solution of sodium hydrogen carbonate is added in instruction 2 and name the gas produced in this step.
(ii) Explain why anhydrous sodium sulfate is added in instruction 3.
(iii) Name the process used in instruction 4 to purify the organic product. Write the number of the equipment that a student would use to perform this process from the diagrams below.
(iv) Discuss the process carried out in instruction 4 on page 6. Include in your answer:
• the purpose of this process
• an explanation of how it works.
Discuss the laboratory procedures used to convert butan-1-ol into butanal, and butan-1-ol into butanoic acid. In each discussion, you should:
• outline the process for each conversion
• state and justify the type of reaction occurring
• identify the reagents used, and explain any observations made.
i) Refluxing is often required in reactions involving organic substances. Circle the letter of the apparatus below that would be used in this procedure.
ii) Discuss why refluxing is sometimes used.
A description of a laboratory procedure that could be used for the preparation of 2-chloro-2-methylbutane from 2-methylbutan-2-ol, is given in the table below.
Discuss this procedure by:
(i) explaining why the following reagents are used
- concentrated HCl
- sodium hydrogencarbonate (NaHCO3)
- anhydrous sodium sulfate (Na2SO4)
(ii) justifying the use of the apparatus pictured in terms of the properties of the compounds involved
- separating funnel
- distillation apparatus
Propan-1-ol can be oxidised to produce two different products.
Discuss how to carry out the oxidation of propan-1-ol in the laboratory to obtain two different organic products. The method may use two different samples of propan-1-ol to form each product.
a) A student thoroughly mixed 20 mL of concentrated hydrochloric acid with 10 mL of 2-methylpropan-2-ol.
i) Describe any observation that could be made as a result of the reaction occurring.
ii) Draw and name the structure of the organic product.
b) In the preparation, the impure organic product was initially separated from the reaction mixture. Aqueous sodium carbonate was added to the organic product and when reaction ceased, the organic product was again separated. Anhydrous magnesium sulfate was added to the organic product, which was then transferred to a flask and purified by distillation.
i) Explain why each of the substances identified in bold above was added.
ii) The diagrams below show four different experimental arrangements of equipment.
Using one or more of the sets of apparatus shown, discuss how each of the separation processes, identified in italics above, is carried out.
The sequence below summarises, in part, the reactions for the preparation of an organic compound, F.
a) Draw and name the structure of an ester molecule that is a structural isomer of compound C above.
b) Compound A can be directly converted to compound C by adding an oxidising agent and heating the mixture under reflux.
• Identify an appropriate oxidising agent, and
• select one of the diagrams below and use it to explain (in the space below) how the process of reflux works, and why the reaction is carried out this way.
c) The conversion of compound A into compound C initially involves formation of compound B.
i) Draw the structural formula of compound B and name it.
ii) Describe how the conditions in part (b) could be modified to produce compound B rather than compound C as the major product. Give reasons for these modifications.
d) Compound C is reacted with PCl5 under anhydrous conditions to form compound D.
i) Draw the structural formula of compound D and name it.
ii) What is meant by ‘anhydrous conditions’ and explain why such conditions are necessary for this reaction.
e) i) Name compound E.
ii) Identify reagent G.
f) Compound E can be hydrolysed by reaction with aqueous sodium hydroxide. Name the products of this hydrolysis reaction and draw the structural formula for each.
i) Draw the monomer(s) from which this polymer is formed. ii) Discuss the hydrolysis of the polymer.In your answer you should include: • the conditions under which it can be hydrolysed • structures of the organic products formed as a result of hydrolysis.
3.5 AS91391 Demonstrate understanding of the properties of organic compounds (5 credits)
IUPAC NAMING
NCEA PAST EXAM QUESTION: Write the IUPAC (systematic) names for the following organic substances
The tables below provide an overview of the molecules and year that they appeared in the NCEA Exam paper
The structure of aspartame (artificial sweetener) is given below. Identify the FOUR different functional groups within the aspartame molecule that are circled
Click on the solution and reasons for incorrect alternative IUPAC names here
NCEA PAST EXAM QUESTION: Draw the structural formula (aka displayed or expanded structural formula) for the following organic substances
The table below provides an overview of the names of the organic substance and year that they appeared in the NCEA Exam paper
ISOMERS
NCEA PAST EXAM QUESTIONS on constitutional isomers and stereoisomers
Alanine is an amino acid. Its structure is shown below.
(a) (i) Describe the structural feature necessary for a compound to exist as enantiomers (optical isomers).
(ii) Identify one physical property that is the same for both enantiomers of alanine, and one that is different, clearly describing how this property could be used to distinguish between the enantiomers.
(b) Draw 3-D structures of the enantiomers of alanine.
When butan-2-ol undergoes a reaction with concentrated H2SO4, three possible organic products form, which are isomers of each other.
i) Draw the three isomers formed during this reaction.
ii) Which of the three isomers from part (i) will be formed in the smallest amount? Explain your answer.
a) The alcohol below can exist as two enantiomers (optical isomers).
i) Draw three-dimensional structures for the two enantiomers.
ii) Link the structure of enantiomers to a physical property that can be used to distinguish them from non-optically active molecules.
b) Draw the structural formulae of three different isomers of
• Isomer 1 turns moist blue litmus paper red.
• Isomer 2 is an ester.
• Isomer 3 is a ketone.
1) The amino acid alanine below can exist as two enantiomers (optical isomers).
i) Draw three-dimensional structures for the two enantiomers that clearly show the relationship between them.
ii) Alanine has two straight chain isomers that do not show acidic properties. One of these isomers, P, can exist as an enantiomer, the other isomer, Q,cannot. Draw P and Q.
iii) Explain why P exists as an enantiomer.
The amino acid alanine below can exist as two enantiomers (optical isomers).
i) Draw three-dimensional structures for the two enantiomers that clearly show the relationship between them
ii) Alanine has two straight chain isomers that do not show acidic properties. One of these isomers, P, can exist as an enantiomer, the other isomer, Q,cannot. Draw P and Q.
An alcohol A with the molecular formula C4H10O can exist as enantiomers (optical isomers).
i) State the structural requirement for a molecule to be able to exist as enantiomers.
ii) Describe a property of enantiomers that would enable them to be distinguished from each other.
iii) Draw the structural formulae of the enantiomers of alcohol A.
Compound A is a carboxylic acid with the molecular formula C4H8O2.
i) Draw the structural formula for the isomers of Compound A (they are an alkene, aldehyde and ester)
ii) Identify an isomer of Compound Athat can exist as a pair of enantiomers (optical isomers) and justify your choice
i) Draw a circle around the product of the reaction below that will show optical isomerism (exist as enantiomers). Give a reason for your answer.
ii) Explain how the two enantiomers of the compound circled above could be distinguished from each other.
a) C5H11OH is an example of an alcohol that can exist as a number of different isomers. Draw structures of the isomers of C5H11OH that satisfy the requirements of i) a branched-chain secondary alcohol (A) and ii) a branched-chain tertiary alcohol (B)
b)Explain why
is the only primary alcohol isomer of C5H11OH that is able to exist as a pair of enantiomers (optical isomers).
i) Draw structural formulae for all the possible constitutional (structural) isomers of C4H10O that are alcohol
ii) Circle any isomer above that can exist as a pair of enantiomers (optical isomers).
iii) Explain what physical property would allow the two enantiomers to be distinguished.
Lactic acid is the common name for 2-hydroxypropanoic acid. Lactic acid can exist as enantiomers (optical isomers)
a) Draw three-dimensional structures for the two enantiomers of lactic acid that clearly show the relationship between them.
b) Compound X is a structural isomer of lactic acid. Compound X will turn blue litmus red but cannot exist as enantiomers.
i) Draw the structural formula for Compound X.
ii) Explain why this structure cannot exist as enantiomers
An alcohol (C4H10O) can exist as optical isomers (enantiomers).
i) Draw three-dimensional structures that show the relationship between the two enantiomers.
ii) Draw and name a structural (constitutional) isomer of
iii) Discuss the differences in chemical and physical properties between samples of these two structural isomers.
a) Compound A is an isomer of C4H8O and can exist as two enantiomers (optical isomers). It contains two different functional groups – an alcohol(OH–) group and an alkene group. Draw 3-dimensional structures for both enantiomers that clearly show the relationship between them.
b) Two compounds (B and C) have the same molecular formula, C4H8O. They are cis-trans isomers that contain a primary alcohol group. Both compounds rapidly decolourise bromine solution. Draw the structural formulae of compounds B and C.
i) Compound
can exist as two optical isomers (enantiomers).
Draw 3dimensional structures that clearly show the relationship between the two enantiomers.
ii) Describe similarities and differences in the chemical and physical properties of the enantiomersPOLYMERS - general questions
NCEA PAST EXAM QUESTIONS on Polymers
A form of the polymer nylon can be made from the two monomers below.
(i) Draw the repeating unit of the polymer formed if these two monomers are used Consider the formation of this form of nylon in a laboratory.
(ii) Describe the type of reaction occurring, and explain why this reaction results in a polymer.
(iii) Explain why sebacoyl chloride is dissolved in a non-polar organic solvent rather than in water
(iv) Elaborate on the reaction that will occur if a dilute aqueous solution of acid is mixed with the newly formed polymer.
The following polymer will, under the correct conditions, hydrolyse.
i) Draw the monomer(s) from which this polymer is formed.
ii) Discuss the hydrolysis of the polymer.In your answer you should include:
• the conditions under which it can be hydrolysed
• structures of the organic products formed as a result of hydrolysis.
The structures of Polymer A and Polymer B are given below.
a) Draw the monomers from which these polymers are made.
b) One of the polymers from above can be hydrolysed using NaOH(aq). Identify the polymer and draw structures for the organic products of the hydrolysis.
c) Nylon 6,10 can be made from the monomers below.
Steps for the formation of Nylon 6,10 are given below:
1. 2 g of the diamine is dissolved in 25 mL of water.
2. 2.5 mL of sebacoyl chloride is dissolved in 25 mL of a non-polar organic solvent.
3. The dissolved sebacoyl chloride is poured into the diamine solution.
4. 5 g of NaHCO3 is added.
5. The nylon is extracted from the interface between the diamine and sebacoyl chloride layers.
• Identify the repeating unit of the polymer formed
• Explain why the diamine is water soluble.
• Explain why the sebacoyl chloride is dissolved in a non-polar organic solvent.
• Explain why NaHCO3 is added.
a) Nylon 6,6 is a polymer with the following structure:
i) Circle an amide linkage in the structure above.
ii) Draw TWO monomers that could have formed this polymer.
b) Nylon 6 is formed from the monomer H2N–(CH2)5–CO2H.
i) Name this monomer and draw THREE repeating units of the Nylon 6 polymer chain
ii) Nylon is used for making ropes for climbing and abseiling. The ropes come with a warning label attached, such as that shown below.
Discuss why this warning label is attached to nylon rope when purchased.
Include in your answer:
• the type of reaction that would occur
• relevant organic structural formulae
• any changes to the properties of the nylon rope.
The polymer commonly known as Kevlar is used to make bullet-proof vests and bicycle tyres. It can be made in a condensation reaction from either of the following pairs of monomers:
However, the second pair of monomers needs to be heated for the polymerisation reaction to take place.
Discuss these polymerisation reactions.
Your answer should include:
• a repeating unit of the polymer chain
• reasons for the choice of monomers
• identification of the functional group in the polymer
• a reason why this is classified as a condensation reaction
• a comparison of the two pairs of monomers, including the reason that the second reaction will not take place without heating.
a) Kodel is a polymer with the following structure:
i) Identify TWO monomers for this structure.
ii) Explain why this type of polymer is known as a condensation polymer.
b) Compound X is a polymer which can be hydrolysed to give a single monomer, Compound Y, which has the molecular formula C3H6O3.
Draw a section of the polymer, Compound X, showing at least two repeating units.Lactic acid
is able to form a condensation polymer in the presence of dilute sulfuric acid. Draw three repeating units of this polymer.
a) The reaction scheme below shows formation of a section of a nylon polymer chain. Complete the reaction scheme by:
i) identifying reagents 1, 2 and 3,
ii) drawing the structures of compounds P and Q,
iii) drawing a single repeating unit for the nylon polymer formed.
b) Nylon is used as a fibre to manufacture ropes and fabrics. These products can be damaged if they come into contact with acidic solutions.
Teflon is a polymer formed from F2C=CF2 and is not affected by contact with acidic solutions.
Discuss why nylon is affected by acidic solutions while Teflon is not. Use structural formulae and equations where appropriate.
Consider the following statement.
"Polyesters are polymers that can be made from two different monomers or from a single monomer"Discuss this statement, using the structures of specific monomers and the polyesters that can be made from them, to illustrate your answer. Your answer should demonstrate a clear understanding of the highlighted terms.
AMINO ACIDS, DI- AND TRI-PEPTIDES AND PROTEINS
Glycine and alanine can combine together with the elimination of a molecule of water to produce a dipeptide – as shown below
Look carefully, you’ll notice that glycine and alanine can combine to form a different dipeptide because a -H can be removed from the glycine and –OH from the alanine to from a different dipeptide and a water molecule. If three amino acids are joined together eg three molecules of glycine a tripeptide is formed.
If lots of amino acids are joined together (as in a protein chain), a polypeptide is formed.
NCEA PAST EXAM QUESTIONS on Amino Acids, dipeptides, tripeptides and proteins
Peptides are formed when amino acids combine.
(i) show two possible dipeptides that can be formed by combining the amino acids:
(ii) Circle the amide link in each dipeptide.
a) Glycine and serine are two amino acids, which can combine to form dipeptides.i) Draw the structure(s) of the possible dipeptide(s) formed from a combination of glycine and serine.
ii) Explain your answer in terms of the structure and functional groups present in the amino acids and in the dipeptide(s).
b) Determine the products of hydrolysis of the molecule shown below in BOTH acidic and basic conditions. Justify your answer in terms of structure and reactivity.
Amino acids are the building blocks that make up proteins. Alanine and valine are amino acids which can combine to form dipeptides.
a) Draw the structure of a possible dipeptide formed from the combination of alanine and valine.b) Draw the organic products of the hydrolysis of the dipeptide below using : i) dilute hydrochloric acid solution ii) dilute sodium hydroxide solution.
a) Gluthathione (GSH) is one of the most common small peptides in animals, plants and bacteria
ii) Draw structures of the products of the hydrolysis of this compound using alkaline conditions (NaOH) and compare with the structures of the hydrolysis products under acidic conditions.
Compound
i) Draw the structural formulae for the two possible dipeptides.
ii) Explain why the formation of dipeptides is referred to as a ‘condensation reaction’.
ESTERS and TRIGLYCERIDES
A triglyceride has the following structure:
(i) Circle one of the alkene groups in the triglyceride molecule.
(ii) This triglyceride is described as unsaturated. Describe a chemical test that can be used to show that the molecule is unsaturated. Give any observations, and state the type of reaction occurring.
(iii) Draw the structural formulae of the organic products formed by hydrolysis of this triglyceride using aqueous sodium hydroxide.
The triglyceride below is shown in condensed form.
(ii) Compare and contrast the reaction of the above triglyceride when it undergoes both acidic and basic hydrolysis. In your answer you should include:
• drawings of condensed structures of the organic products
• any reagents and conditions required for the reaction to proceed.
Give the structures and names of the products of the reactions below. These reactions are carried out by heating in either:
• dilute hydrochloric acid solution, or
• dilute sodium hydroxide solution.
Discuss the similarities and differences in the reactions of methyl propanoate, CH3CH2COOCH3, in basic conditions with NaOH, and in acidic conditions with HCl.
In your answer you must:
• describe the type of reaction
• write equations showing structural formulae for reactions occurring.
A triglyceride found in olive oil has the following structure:
i) Put a circle around one of the ester groups in the triglyceride molecule shown above.
ii) This triglyceride is described as being an unsaturated molecule, which means that it contains carbon to-carbon bonds, which are not single bonds.
Bromine water can be used to confirm that this triglyceride is unsaturated. Describe the observations when bromine water is reacted with this triglyceride.
iii) Draw the structural formulae of the products produced by the hydrolysis of this triglyceride in basic conditions, using aqueous sodium hydroxide, NaOH.
i) For the molecule below, circle the ester functional group and put a square around the alkene functional group.
ii) Complete the equation below to show the structural formulae of the two organic reactants used in the preparation of 2-methyl propenoate.
iii) 2-methyl propenoate will react with HCl to give two different haloalkane products. Draw the structural formulae of the haloalkane products.
1) Esters are often responsible for the flavouring of fruit. The compound below is an ester with a raspberry flavour.
Esters can be prepared by refluxing the reactants with a small amount of concentrated sulfuric acid. After refluxing, the reaction mixture is treated with potassium carbonate and distilled.
Discuss the preparation of the ester shown above. Your answer should include:
• an appropriate chemical equation for the formation of the ester
• the reason for using the chemicals stated in bold above
• a discussion of why reflux and distillation are used in this preparation.
2) The triglyceride shown below was heated with aqueous sodium hydroxide, NaOH. Draw the structural formulae of the two products formed in this reaction.
A triglyceride found in cocoa butter has the following structure.
a) Complete the equation below, which shows hydrolysis of this triglyceride in acidic conditions using H2SO4 solution.
b) Compare the products that would form if the hydrolysis occurred in basic conditions using NaOH solution
Palm oil contains the triglyceride with the structure shown below. It forms when glycerol (an alcohol) and palmitic acid (a carboxylic acid) react together.
a) Use the diagram above to deduce the structural formulae of glycerol and palmitic acid. Draw them in the spaces below.
b) The triglyceride shown above can undergo hydrolysis in acidic or basic conditions. How will the different hydrolysis conditions affect the products of the reaction?
Fats and oils are triester molecules. Hydrolysis of a fat can be represented by the equation below.
a) Circle ONE of the ester groups in the fat.
b) Write the name of the functional group that would be present in compound M.
c) Unsaturated fats are usually considered to be healthier than saturated fats. What is meant by the term unsaturated?
d) Describe a test, using a solution of bromine in a non-polar solvent, that could be carried out in the laboratory to compare the degree of unsaturation of two fats.
DISTINGUISHING BETWEEN ORGANIC SUBSTANCES
NCEA PAST EXAM QUESTION: Distinguishing between organic compounds
Identify the reagents, conditions required, and observations linked to species, to enable the following pairs of chemicals to be distinguished from each other.
(i) Aqueous solutions of propanamine and propanamide.
(ii) Propanone and propanal.
(iii) Propanoyl chloride and propyl propanoate.
1) Devise a method for distinguishing between the three liquid compounds, butan-1-ol, butanoic acid, and butanoyl chloride, using only blue litmus paper and water.
Explain each of the observations in your method, with reference to the structure of the organic compounds.
2) Describe how you could distinguish between methylpropan-2-ol and butan-1-ol and butan-2-ol , using chemical tests on the alcohols and / or their oxidation products
Explain a laboratory procedure that would allow the following pairs of compounds to be distinguished. In your answers, you should include:
the reagent used
the expected result for any reactions that may or may not occur
the structural formulae of the organic product(s) formed when the reaction(s) occur.
Explain a laboratory procedure that would allow the following pairs of compounds to be distinguished. In your answers, you should include:
the reagent used
the expected result for any reactions that may or may not occur
the structural formulae of the organic product(s) formed when the reaction(s) occur.
Describe a test that could distinguish between an amide and an amine
1) Explain how you could distinguish
from propanone 
Your explanation should include:
• the reagents used and the conditions needed
• the expected observations.
2) Compound X, an isomer of Compound A, C3H6O3, can exist as enantiomers. It reacts with acidified dichromate solution to give Compound Y, C3H4O3. Both compounds X and Y react with sodium carbonate to produce carbon dioxide gas. Identify Compounds X and Y and justify your answers in relation to the information above.
1) A colourless liquid is known to be a branched-chain alcohol with the molecular formula C5H11OH. Investigations of this liquid show the following
features:
• It does not rotate the plane of polarised light.
• It reacts with acidified potassium dichromate solution.
• It reacts with concentrated sulfuric acid. The product of this reaction decolourises bromine water.
Use the features listed to determine which of the alcohols A to E is the colourless liquid. Justify your answer.
2) Devise a method for distinguishing between propanoyl chloride, 2-amino-3-methylbutane, pentanal, 4-chlorobutanoic acid. Each test should use either moist red litmus paper or an acidified solution of potassium permanganate
Discuss how to test propanal and propanoic acid to demonstrate that they are different from each other AND different from propan-1-ol. Include the observations that would allow each substance to be identified as a result of these tests.
1) The identity of a colourless liquid is unknown. It is thought to be one of the following: ethanoyl chloride (CH3COCl) or ethanol (CH3CH2OH) or 2-methyl propan-2-ol ((CH3)3COH) or hex-1-ene (CH2= CHCH2CH2CH2CH3).
Devise a scheme using bromine water and acidified dichromate to identify the colourless liquid.
Describe the observations expected at each stage (equations not required).
Describe a chemical test that would distinguish between each of the following pairs of substances. For each test, identify the reagents used, and link the observations to any reactions that may or may not occur.
Describe chemical tests that could be used to distinguish between the compounds in each of the pairs of substances below. For each test description:
• include reagents used, and
• link the observed results to the reactions occurring at the functional groups present in the organic molecules.
Do NOT use the same test more than once.
There is no Crystal Ball Activity for Level 3 distinguishing between organic substances because once you have complete all the questions above you'll be sweet with them.
Organic reaction pathways
Download, print the charts above, then stick to the back of your toilet door, take a break, clear a blockage and learn your Organic Reaction pathways
NCEA PAST EXAM QUESTIONS on Reaction pathways and reagents
Complete the following reaction scheme by drawing the structural formulae of the organic compounds A to E, and identifying reagents 1 to 5.
Propene can be reacted with water in the presence of acid to form a major product (A) and a minor product (B).
• A is oxidised to form product C.
• B is oxidised to form product D.
• When D is reacted with SOCl2, it forms product E.
• When D is reacted with alcohol B, it forms an ester G.
• When D is reacted with alcohol A, it forms ester H, which is an isomer of G.
• When E is reacted with alcoholic ammonia, it forms product F.
• When E is reacted with water, it forms product D.
1) For the following conversions, identify the reagent required, and state the type of reaction occurring.
(i) Pentan-2-one is converted to pentan-2-ol.
(ii) Butan-2-ol is converted to a mixture of but-1-ene and but-2-ene.
(iii) Discuss the reaction occurring in (ii) above, with reference to the structures of the organic reactant and products.
2) Complete the following reaction scheme by drawing the structural formulae of the organic compounds B and C, and identifying reagent 1.
Include any necessary conditions, needed to bring about the transformation from reactant A to the organic compound C, which is a base.
When ammonia reacts with
two products are formed. Complete the equation below by naming compounds or drawing the structure.
1) For the following conversion, identify the reagent required and state the type of reaction occurring. You should give a reason for your answer in terms of the structure of the reactants and products.
b) Devise and complete the reaction scheme starting with butanone in place of butanal to show how butanone would react with the reactants 1–3. In your answer, you should:
identify the products formed in each reaction step; state if no reaction occurs
write the structural formula for each product formed, including major and minor products (if any).
c) Compare and contrast the two reaction schemes. In your answer, justify the reasons for
the similarities and the differences between these two schemes
the products formed in each reaction.
4) Use the following information to answer this question.
Compound W is a branched chain molecule with a molecular formula C4H10O. When Compound W is heated with excess acidified potassium dichromate it is readily oxidised to Compound X, which has acidic properties A substitution reaction occurs when Compound X is reacted with SOCl2. The molecular formula of Compound Y isC4H7OCl When Compound Y reacts with aminomethane, CH3–NH2, a substitution reaction occurs and Compound Z forms
Determine the structural formulae of Compounds W, X, Y, and Z.
Justify your answer by explaining how you arrived at these structures from the information given above. In your answer, you should:
include other possible structural formulae you considered
give your reasons for rejecting the other structural formulae.
1) The haloalkane 1-chlorobutane can be used to make butanamide. One of the intermediate products is a carboxylic acid. Show, using structural formulae, how this might be achieved in a number of reaction steps. Include all reagents
2) Alcohol A, (C4H10O) can react with Cr2O72– / H+ to give compound B which does not react with Tollens’ reagent. Compound A also reacts with SOCl2 to give a haloalkane C, which when reacted with alcoholic KOH, gives two products, D and E, which are not geometric isomers. When E reacts with H+ / H2O, A is the product. When D reacts with H+ / H2O, two products are formed, A and F. F can be oxidised to form butanoic acid. Give the structural formulae AND names for each of the compounds A to F.
Complete the following reaction scheme by naming and drawing the structural formula of each of the compounds A to F. Identify the reagents 1 to 4, including any necessary conditions, needed to bring about each transformation.
The haloalkane, 2-chloro-2-methylbutane, can be prepared by reacting 2-methylbutan-2-ol with concentrated HCl.i) Write an equation for this reaction using structural formulae.ii) State the type of reaction occurring, and give a reason for your answer.
1) Identify the compound from these given: propanoyl chloride, 2-amino-3-methylbutane, pentanal, 4-chlorobutanoic acid that will react as described below, and draw the structural formula for each organic product formed.
Elimination with alcoholic KOH
Oxidation with Fehling’s or Benedict’s solution
Substitution with aqueous KOH
2) Complete the reaction scheme by giving the formulae for reagents 1 to 4 and the structural formulae for the organic products A to D.
Complete the following reaction scheme by giving the formulae for reagents 1 to 5 and the structural formulae for the THREE organic products.2-bromobutane reacts by substitution to form 2-butanol. However, if the reaction conditions are changed, an elimination reaction occurs. There are two possible products for the elimination reaction. Complete the following reaction scheme by indicating the reagents in the shaded boxes and the organic products in the other boxes for each of these reactions of 2-bromobutane.
Complete each of the equations below by writing the organic product in the blank boxes and the reagent needed in the shaded boxes.
For each reaction below, identify: (i) the type of reaction, (ii) the reagent required to carry out the reaction.
a) Complete the reaction scheme below by:
i) identifying the three reagents
ii) drawing the structures of compounds X and Y
iii) naming organic compounds X and Y, and the compound with formula CH3CH2COCl
b) Each of the parts (i) – (iii) below refers to one step in the reaction scheme on page 2. For each part, identify the type of reaction (from the given list: addition, elimination, oxidation, polymerisation, substitution) and use the reaction in that step to explain the term.
i) 2-chloropropane is converted to propene.
ii) Compound X (the minor product) is converted to propan-1-ol.
iii) Propan-1-ol is converted to propanoic acid.
c) When HBr is reacted with propene, there are two possible products. Discuss how the compounds formed in this reaction scheme would vary if these two products were not separated before reagent 2 is added
.
The following reactions involve the loss of water. Clearly show the structure of one major organic product of each of these reactions.
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NCEA PAST EXAM QUESTION: Describe and Explain Practical Procedures in Organic Chemistry
Explain why the equipment below is used for hydrolysis of a triglyceride.
Instructions for the preparation of 2-chloro-2-methylpropane are given below. Read the instructions carefully and answer the questions that follow.
1. Shake 10 mL of 2-methylpropan-2-ol with 30 mL of concentrated hydrochloric acid in a separating funnel for 10 minutes.
2. Run off the bottom acid layer and discard it. Add saturated sodium hydrogen carbonate to the organic product. Shake, releasing the tap every few seconds to relieve the pressure.
3. Run off the bottom aqueous layer and discard it. Transfer into a conical flask and add some anhydrous sodium sulfate, and stir thoroughly.
4. Transfer the organic product into a round-bottom flask, and collect the fraction boiling within 2oC of the boiling point of 2-chloro-2-methylpropane.
(i) Explain why the solution of sodium hydrogen carbonate is added in instruction 2 and name the gas produced in this step.
(ii) Explain why anhydrous sodium sulfate is added in instruction 3.
(iii) Name the process used in instruction 4 to purify the organic product. Write the number of the equipment that a student would use to perform this process from the diagrams below.
(iv) Discuss the process carried out in instruction 4 on page 6. Include in your answer:
• the purpose of this process
• an explanation of how it works.
Discuss the laboratory procedures used to convert butan-1-ol into butanal, and butan-1-ol into butanoic acid. In each discussion, you should:
• outline the process for each conversion
• state and justify the type of reaction occurring
• identify the reagents used, and explain any observations made.
i) Refluxing is often required in reactions involving organic substances. Circle the letter of the apparatus below that would be used in this procedure.
A description of a laboratory procedure that could be used for the preparation of 2-chloro-2-methylbutane from 2-methylbutan-2-ol, is given in the table below.
(i) explaining why the following reagents are used
- concentrated HCl
- sodium hydrogencarbonate (NaHCO3)
- anhydrous sodium sulfate (Na2SO4)
(ii) justifying the use of the apparatus pictured in terms of the properties of the compounds involved
- separating funnel
- distillation apparatus
Propan-1-ol can be oxidised to produce two different products.
Discuss how to carry out the oxidation of propan-1-ol in the laboratory to obtain two different organic products. The method may use two different samples of propan-1-ol to form each product.
a) A student thoroughly mixed 20 mL of concentrated hydrochloric acid with 10 mL of 2-methylpropan-2-ol.
i) Describe any observation that could be made as a result of the reaction occurring.
ii) Draw and name the structure of the organic product.
b) In the preparation, the impure organic product was initially separated from the reaction mixture. Aqueous sodium carbonate was added to the organic product and when reaction ceased, the organic product was again separated. Anhydrous magnesium sulfate was added to the organic product, which was then transferred to a flask and purified by distillation.
i) Explain why each of the substances identified in bold above was added.
ii) The diagrams below show four different experimental arrangements of equipment.
Using one or more of the sets of apparatus shown, discuss how each of the separation processes, identified in italics above, is carried out.
The sequence below summarises, in part, the reactions for the preparation of an organic compound, F.
b) Compound A can be directly converted to compound C by adding an oxidising agent and heating the mixture under reflux.
• Identify an appropriate oxidising agent, and
• select one of the diagrams below and use it to explain (in the space below) how the process of reflux works, and why the reaction is carried out this way.
c) The conversion of compound A into compound C initially involves formation of compound B.
i) Draw the structural formula of compound B and name it.
ii) Describe how the conditions in part (b) could be modified to produce compound B rather than compound C as the major product. Give reasons for these modifications.
d) Compound C is reacted with PCl5 under anhydrous conditions to form compound D.
i) Draw the structural formula of compound D and name it.
ii) What is meant by ‘anhydrous conditions’ and explain why such conditions are necessary for this reaction.
e) i) Name compound E.
ii) Identify reagent G.
f) Compound E can be hydrolysed by reaction with aqueous sodium hydroxide. Name the products of this hydrolysis reaction and draw the structural formula for each.
i) Draw the monomer(s) from which this polymer is formed.
ii) Discuss the hydrolysis of the polymer.In your answer you should include:
• the conditions under which it can be hydrolysed
• structures of the organic products formed as a result of hydrolysis.